Global Warming or Little Ice Age: Which Will It Be?

Below:

Next story in Science

Our sun may be on the verge of a relatively long snooze, as
researchers have found solar energy output could decrease in the
coming decades. Though the dip in solar activity isn't expected
to reverse climate change and plunge Earth into a cold snap,
similar phenomenon have happened in our planet's history,
scientists say.

Some researchers say that changes in
sun activity caused the "Little Ice Age" from 1500 to 1800 —
during the chilliest part of this cooling trend beginning in
1645, the sun reached its 75-year Maunder Minimum, when
astronomers found almost no sunspots. But the connection between
solar activity and Earth's climate remains largely mysterious —
scientists are not sure how much of a role the Maunder Minimum
played in fueling the little ice age.

And despite media claims in recent days that global cooling is
imminent, experts don't expect a repeat of the little ice age
anytime soon.

"It turns out this would be a very minor impact on the climate,
even if we were to return to Maunder Minimum conditions," climate
scientist Michael Mann, of Pennsylvania State University, told
LiveScience. "That would only lead to a decrease in about 0.2
watts of power per square meter of the Earth's surface — that
compared to greenhouse forcing, which is more than 2 watts per
meter squared. That's a factor of 10 larger."

Predicting solar activity

When researchers refer to solar activity, they generally mean the
number and intensity of sunspots, which are dark, cool,
magnetically twisted areas on the sun that sometimes erupt
violently and send streams of charged particles into space. This
activity ebbs and flows in an 11-year cycle.

Even while approaching the next peak in the cycle, a typically
storm period called solar maximum that's due in late 2013, the
sun seems to be entering a
decreased solar output phase, new research has suggested, one
that might all but eliminate sunspot activity during the next
cycle, which hits its maximum again in 2022. The data supporting
this come from three separate analyses of sunspot activity, solar
jet streams and the magnetic field.

"I'm skeptical of all three pieces of evidence that were
presented," said Doug Biesecker, of NOAA's Space Weather
Prediction Center, who notes that the data is based on only a few
years of observations. "We know the sun doesn't behave exactly
the same way all the time, so give the sun a chance to show its
normal behavior before we say it's abnormal."

Fewer sunspots would mean lower sun activity in general, the
researchers who presented the work believe; and they expect fewer
of the suns' intense bright spots called faculae, which ring the
sunspots. This decreased brightness would lower the amount of
energy that reaches the Earth from the sun. But by how much is an
open question.

A new Little Ice Age?

The Little Ice Age that began in the 1500s could have been caused
by decreased solar output of just 0.2 percent, previous
research by Peter Foukal suggests, though he believes that
there were most likely other, earthly factors (including several
erupting volcanoes) at play as well.

"If it really were true that the sun were to descend into a
period of literally no sunspots for tens of years, there's a
possibility that what occurred in the 17th century could occur
again," Foukal, of HelioPhysics Inc., told LiveScience. "But we
can't be sure there is a causal effect, we can't say for sure why
it happened in the 17th century."

Foukal believes that the effect of a solar minimum could help
mitigate some of the global warming we are experiencing, though
he warns that eventually the minimum will end. "It could mitigate
partially if the sun does cool things a little bit, but it's a
matter of time before the sun comes back to life again [and] you
will roast," Foukal told LiveScience.

Even if the sun has reached a new low point in its cycle, the
change in solar output would not be nearly enough to undo even
the current warming we've already experienced from increased
greenhouse gasses in the atmosphere, Mann said.

Predicting solar output

Researchers have a tough time predicting changes in solar output,
though scientists include in their climate simulations the little
information they have about solar changes. The known
11-year-cycle is already built into their climate
predictions, though it's difficult to know how active any given
cycle will be.

A paper published last year by Georg Feulnerand Stefan
Rahmstorf (of the Potsdam Institute for Climate Impact
Research in Potsdam, Germany) in the journal Geophysical Research
Letters tried to use these models to predict what would happen if
the sun did actually enter a new Maunder Minimum starting in
2030. The model found the numbers that agreed with those quoted
by Mann — a decrease of 0.2 watts of power per meter, which is
the equivalent of 0.2 degree Fahrenheit (0.1 degree Celsius) of
cooling.

"The influence of the grand solar minimum is to decrease the
effect of the greenhouse gasses by a few tenths of a degree,"
Mann said about the results of that study. "How much of a player
compared to other drivers that we know are important? It's almost
down in the noise, it's a blip on the radar screen."

While admitting that a small decrease in warming could happen,
Mann doesn't agree that it could send Earth into another Little
Ice Age. "It's ludicrous, there is no scientific support for that
whatsoever," Mann said. "The science doesn't even remotely
support that conclusion."

Mann believes that the temperature changes during the Little Ice
Age were mainly caused by several volcanic eruptions during that
time, which changed the temperatures and dynamics of the
atmosphere, causing localized cooling.

Changes to the jet stream also affect local temperatures, as it
moves cooler air upward across Europe. The jet stream is
dependent on ozone levels in the atmosphere, which in turn can be
affected by either solar radiation or by volcanic output in the
atmosphere. The debate still rages as to how big of an effect
each of these factors play.

You can follow LiveScience staff writer Jennifer Welsh on
Twitter @microbelover.
Follow LiveScience for the latest in science news and discoveries
on Twitter@livescienceand onFacebook.